While it is well documented that children with autism are impaired in their language development, research on their categorization has shown little to no impairment. However, such research has focused only on children's categorization using perceptual features of objects and not considered what role causality plays in conceptual development. This project seeks to examine conceptual and language development in both normal children and children with autism, focusing on their causal understanding of the world. Furthermore, conceptual development has usually been related to aspects of language development. It is possible that understanding categorization using causal features of objects is related linguistically to providing causal explanations about the world. Children between the ages of 24 months and 6 years will be given categorization tasks that use causal and perceptual cues. They will also be given narrative tasks, designed to elicit explanations about the world. Children with autism of certain ages will also be tested. In this way, we can discover if the linguistic and conceptual developments are linked and what role they might play in diagnosis and treatment.